Weak, sulphated or ageing Battery B that can no longer hold or accept charge properly; Loose, corroded or damaged battery terminals, earth straps or connectors causing false voltage or current readings; Faulty battery current, voltage or temperature sensor feeding the state of charge calculation; Charging system fault, such as a weak alternator, DC-DC converter or charger, so Battery B is not charged correctly; Excessive parasitic drain or a recent battery replacement or disconnection without the system relearning battery data; Fault in the battery management module or control unit, or its wiring and communication.

P00FD

Battery B State of Charge Performance.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
0: AreaFuel and air metering, auxiliary emission controls
FD: FaultThe specific fault in that area

What it means

P00FD means the control unit has judged that the state of charge of 'Battery B' is not behaving as expected. Battery B is the second or additional battery in the system, such as an auxiliary 12V battery or a hybrid or secondary traction battery, and which one it is depends on the model. The code usually sets when the calculated or measured state of charge is out of range, does not respond properly to charging or discharging, or disagrees with other readings such as voltage, current or temperature.

Symptoms

Battery or charging warning light on the dashboard
Engine or hybrid system warning light (MIL) on
Slow cranking or intermittent no-start
Start-stop or hybrid assist functions disabled or reduced
Battery charge indicator reading oddly or fluctuating
Electrical features behaving erratically or shutting down

Possible causes

Weak, sulphated or ageing Battery B that can no longer hold or accept charge properlylikely
Loose, corroded or damaged battery terminals, earth straps or connectors causing false voltage or current readingslikely
Faulty battery current, voltage or temperature sensor feeding the state of charge calculationpossible
Charging system fault, such as a weak alternator, DC-DC converter or charger, so Battery B is not charged correctlypossible
Excessive parasitic drain or a recent battery replacement or disconnection without the system relearning battery datapossible
Fault in the battery management module or control unit, or its wiring and communicationrare

How to diagnose

Read all stored and pending codes and freeze frame data, and note any related charging, battery sensor or communication codes
Identify which battery is 'Battery B' on this model using the manufacturer's wiring and system information, as this varies by vehicle
Inspect Battery B, terminals, fuses, earths and connectors for corrosion, looseness, heat damage or water ingress
Measure resting battery voltage and carry out a proper load or conductance test on Battery B
Check charging voltage and current with the engine running or the charging system active, and compare with specification
Monitor live data for state of charge, voltage, current and temperature, and check for sensor values that are implausible or disagree with each other
Check for parasitic drain with the vehicle asleep and look for modules that stay awake
Test the battery sensor or management module circuits for continuity, voltage supply and communication faults

How to fix

Clean and tighten terminals, earths and connectors, and repair any damaged wiring
Replace Battery B if it fails load or capacity testing, using the correct type and specification for the vehicle
Replace a faulty battery current, voltage or temperature sensor, or battery monitoring unit
Repair the charging fault, such as the alternator, DC-DC converter or charger, as found by testing
Trace and repair the cause of any excessive parasitic drain
After repair, clear the code and carry out any battery registration or relearn procedure the manufacturer specifies, then recheck for the fault returning

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but a failing battery may cause a no-start or loss of some electrical or hybrid functions without warning. Get it checked soon, and avoid long journeys until the battery and charging system are tested.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.